1. Field of the Invention
The invention relates to a burner for fluid fuels, particularly oil, natural gas and/or coal gas, of the kind used for gas turbines.
In view of the worldwide efforts to lower the emissions of pollutants from furnace systems, in particular gas turbines, burner configurations have been developed in recent years that have especially low emissions of nitrogen oxides (NOX). Often, emphasis is placed on the capability of such burners to function with not merely a single fuel, but rather with the most varied possible fuels, such as oil, natural gas and/or coal gas, selectively or even in combination, in order to increase the reliability of a fuel supply and flexibility in operation. Such burners are described in European Patent No. 0 276 696 B1, for example.
One problem in constructing burners for all possible, different operating conditions and fuels is that the volumes of the various fuels required for operation in a given case are completely different, which makes it difficult to use the same delivery system and the same injection openings for all fuels. It is therefore known in the prior art to use different delivery systems for liquid and gaseous substances. However, another problem arises then if selective gaseous fuels with completely different specific gross calorific values, such as natural gas and coal gas, are to be used. The completely different volumetric situations when those two fuels are used, and the different chemical processes in their combustion, require modification or expansion of the known systems.
In a published paper entitled "The Development of Integrated Coal-Gasification Combined-Cycle (ICG-GUD) Power Plants" by John S. Joyce, read on Apr. 26, 1990 in Arnheim (a written version was distributed), FIG. 4 describes a burner that is selectively suitable for combusting natural gas or gas with a low specific gross calorific value. In that configuration, however, there is a diffusion burner for both fuels, which in the case of operation with natural gas leads to higher NOX emissions than would be the case with a premixing burner.